Thermal Conductivity of Enhanced High Reflectors

Perkin-Elmer has designed and fabricated a simple thermal conductivity tester for thin film coatings. The work is motivated by the results Don Decker, et al., reported at this conference last year. 1 Our measurements confirm his finding that the thermal conductivity of thin films is substantially less than the thermal conductivity of the corresponding bulk material. In one case the measured thermal conductivity of an enhanced high reflectance coating is a factor of 30 less than the conductivity predicted from bulk values.

Perkin-Elmer has considered the theoretical reasons for the low conductivity, and methods for increasing the conductivity. Increased thermal conductivity should increase the laser damage threshold for CW applications.